1. Field of the Invention
The present disclosure relates to a curl correction apparatus correcting a sheet curl and to an image forming apparatus including the curl correction apparatus.
2. Description of the Related Art
A conventional image forming apparatus such as a copier or a printer includes a curl correction apparatus for removing a sheet curl caused, for example, in a fixing process in which heat and pressure is applied to a sheet.
Japanese Patent Application Laid-Open No. 2002-326753 discusses a curl correction apparatus that corrects a sheet curl by causing a sheet to pass through a nip portion between a drive roller and a pressure roller (a curl correction roller pair). FIGS. 14 and 15 are a perspective view and a side view of the curl correction apparatus discussed in Japanese Patent Application Laid-Open No. 2002-326753, respectively.
The curl correction apparatus in FIGS. 14 and 15 includes pressing force regulating plates 73 for pinching rotation shafts 71a and 72a of a drive roller 71 and a pressure roller 72. By rotating the pressing force regulating plates 73, a pinching portion for pinching the rotation shafts 71a and 72a can be changed among pinching portions 77a, 77b, and 77c. 
In this way, in the curl correction apparatus discussed in Japanese Patent Application Laid-Open No. 2002-326753, since the pressing force regulating plates 73 pinch both of the rotation shafts of the two rollers, the distance between the rotation shafts of the two rollers can be stably maintained, and stable curl removal performance can be obtained. In addition, since the pinching portions 77a, 77b, and 77c has a certain width in a moving direction of the pressing force regulating plates 73, the drive roller and the pressure roller can be adjusted to have a desired pressing force.
However, in the curl correction apparatus discussed in Japanese Patent Application Laid-Open No. 2002-326753, since the pressing force regulating plates 73 pinch both of the rotation shaft 71a of the drive roller 71 and the rotation shaft 72a of the pressure roller 72, the nip between the drive roller 71 and the pressure roller 72 cannot be opened. Thus, if a jam occurs inside the apparatus, it is difficult to remove a jammed sheet. In particular, in a jam clearance operation when an accordion shape jam occurs, the sheet may be torn and part of the torn sheet may be left inside the apparatus, preventing conveyance of subsequent sheets.
There is a possible configuration for improving the jam recovery. That is, by providing an openable conveyance guide with one of the drive roller and the pressure roller and by almost integrally opening and closing the conveyance guide and the roller, the nip between the drive roller and the pressure roller can be opened.
However, with this configuration, it is necessary that each of the drive roller and the pressure roller be held in a different holding portion such as a conveyance guide or a casing. Thus, to maintain a certain distance between the shafts of the drive roller and the pressure roller, higher strength is required for the conveyance guides. In addition, high component accuracy and positional accuracy of latch means are required. Therefore, to increase strength of parts, it is necessary to increase the number of parts and to improve accuracy in processing parts, resulting in an increase of the cost for manufacturing the apparatus.